What are decongestants and antihistamines?
Decongestants relieve a stuffy nose. Antihistamines help
dry up a runny nose. These medicines are often confused
with each other because they are both often used to help
runny, stuffy noses. However, they are different and do not
act the same way on your body.
Many nonprescription cold and allergy products contain
several types of medicines. They may treat many symptoms.
It can be confusing trying to figure out which medicine to
choose. Ask your pharmacist or health care provider if you
are not sure which medicine is best for your symptoms.
How do they work?
Decongestants narrow the blood vessels in the nose. This
reduces swelling. It also reduces the amount of mucous
made by your nose. You can buy some decongestants without a
prescription. The most common types are:
- pseudoephedrine (Sudafed)
- phenylephrine (Neo-Synephrine).
Antihistamines block the effect of histamine. This is a
chemical your body makes when you have an allergic reaction.
It causes redness and swelling. Common antihistamine
medicines are:
- diphenhydramine (Benadryl)
- chlorpheniramine (Chlor-Trimeton)
- cetirizine (Zyrtec)
- fexofenadine (Allegra)
- loratadine (Claritin)
- desloratadine (Clarinex).
When are they used?
Decongestants are often used to treat:
- colds
- ear or sinus infections.
Antihistamines are most often used to treat symptoms of
allergies. These include:
- sneezing and runny nose from hay fever
- itching, swelling, and redness from hives or other
allergic rashes.
What should I watch out for?
Decongestants
If used for too long, decongestants can make your stuffy
nose worse instead of better. They make your blood vessels
smaller so you should not take a decongestant if you have:
- heart disease
- high blood pressure
- glaucoma
- thyroid disease
- trouble urinating or an enlarged prostate
- asthma
- diabetes.
Antihistamines
A common side effect of antihistamines is drowsiness. Some
types are less likely than others to make you drowsy.
Taking antihistamines with other medicines, such as
antidepressants or sedatives, may cause problems. Read the
labels carefully. Ask your provider or pharmacist if you
have any questions.
If you are pregnant, talk with your health care provider
before taking these medicines.


Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File MED4261F.HTM Release 9.0/2006. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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